Possible Clues:

• Neglected to give Billy Bunter another starter
• Ill-kempt
• Poor banker eating tart without filling
• Plunging into river, dry and dishevelled
• What happens on 27 across becomes unkempt in a Scottish river
• Scruffy
• Inferior, scruffy
• River, just about dry, appears untidy
• Worn, scruffy
• Potato sounded to be of poor condition